let inp=document.querySelector('input');
let btn = document.querySelector('#btn');
let sed=60;
btn.addEventListener('click', function(){
    console.log('clicked');
    btn.innerText=60;
    btn.disabled =true;
    // btn.innerHTML = '123';
    var timer=setInterval(function(){
        if(sed===0){
            btn.innerText='发送'
            btn.disabled=false;
        }else{
            --sed;
            btn.innerHTML=sed;
        }
    },1000)
})